“Other” uses 21GB on 32GB IPad

I have 3 IPads (generation 5, 6 and 7) they all are 32GB versions. Two of the iPads have enough storage as the storage category named “other” only uses 2-8 GB, but on one iPad “other” uses 21GB and system 6GB which makes the iPad almost useless. It only have a few apps which can’t update as there are not enough disk space free. Why does this one iPad use so much space as “other” and how to free it up? It just gets worse and worse on this iPad have to delete more and more apps. All images etc are already offloaded to iCloud and most apps are automatically removed to free up space